填空题

请完善程序(程序文件名：Java_1.java)并进行调试。请在下画线处填入正确内容，然后删除下画线。请勿删除注释行和其他已有的语句内容。
题目要求：
请完善程序，程使序运行后输出窗口如下图所示。


源程序：
import javax.swing.*;
import java.text.DecimalFormat;
public class Java_1
public static (1) main(String args[])
SimpleTime t=new SimpleTime(12, 30, 19);
(2) . showMessageDialog(null, t.buildString(), "\" this\”引用示范", JOptionPane. INFORMATION_MESSAGE);
System.exit(0);


class SimpleTime
private int hour, minute, second;
public SimpleTime(int hour, int minute, int second)
this. hour=hour;
this. minute=minute;
this. second=second;

public String buildString()
return "this. toString(): "+ (3) ()+"\ntoString():"+toString()+"\nthis(with implicit toString()call):"+this;

public String toString()
DecimalFormat twoDigits=new DecimalFormat("00");
return twoDigits.format(this.hour)+":"+twoDigits.format(this.minute)+":"+twoDigits.format(this.second);